This invention relates to a tire antiskid apparatus that is used when operating a vehicle on a snow-covered road or icy road, and in practical applications, such apparatus is mounted on each of the driving wheels of the vehicle.
In the past, tire chains have been generally used as a tire antiskid apparatus, and tire chains have a fairly high antiskid effect. Fitting and removal of tire chains, however, require much time and skill, and are difficult jobs when snow covers the ground. As a result, people tend to avoid the use of tire chains.
In recent years, various antiskid apparatuses that allow easier mounting and removal from the tire have been proposed to replace tire chains. Such apparatus include that described in the Japanese Patent Publication No. SHO-58-23241 and one described in the Japanese Provisional Patent Publication No. SHO-63-71401. The former patent shows an apparatus developed by the present inventor, and has a construction wherein a U-shaped fitting which covers the full width of the tire tread is pivotally mounted on each of the free ends of a pantograph or linkage, and a tightener is provided for tightening the linkage between pivotal joints thereof. The latter patent shows apparatus comprising a fixed disc designed to be fixed onto a tire wheel and a support disc having fitting pieces bent to lie along the tire tread, the fitting pieces being mounted on the top end of each antiskid arm and radially extending from the support disc, and the support disc being arranged to be held on the fixed disc by means of a ferrule.
Of the antiskid apparatuses described in the aforementioned two publications, in the case of the former, the antiskid apparatus (in particular, the fittings) is mounted on a tire by means of a plurality of U-shaped fittings arranged at regular intervals over the circumference of the tire tread and the linkage and the tightener that tightens the fittings inwardly. Accordingly, the tightener must be tightened with a relatively strong force when the antiskid apparatus is mounted on a tire. The fittings pose some problems such that, as the fittings are held on the tire tread by the tightening force, the tire tread would slip relative to the fittings when the tightening force is weak, resulting in a deteriorated antiskid effect, and that even when the tightening force is strong, the fittings would slide over the tire thread during braking, resulting in an extended braking distance.
In the case of the latter patent, a plurality of antiskid arms are radially extended from the central support disc. As these arms cannot be folded up, the apparatus requires a fairly large space when it is not in use and is stored in, for example, the trunk of the vehicle, and it is not convenient for carriage. Further, this antiskid apparatus cannot be mounted on a tire of a vehicle wherein the upper portion of the tire is concealed within the tire housing since the anti-skid arms must be placed on the tire from the front of the tire. Moreover, the apparatus cannot be mounted on a tire without spreading a span between two consecutive gripping pieces at the top ends of said antiskid arms to the same length of the ground contact surface of the tire. As a result, the spans between gripping pieces are wide, and the actual total length of the gripping pieces arranged over the tire tread is short (less than one-half of the whole circumference of the tire), thus giving a slightly smaller antiskid effect. The apparatus also has problems in that the connecting structures between the fixed disc secured to a tire wheel, the support disc for support arms of the antiskid pieces, and the ferrule for securing the support disc onto the fixed disc are very complex and require lengthy processes of fabrication, and consequently the production costs are high.